Vol. 19, No. 2, Page 14

APPLICATIONS

FIBRE REINFORCEMENT Acrylics (polymethyl methacrylate) are inherently brittle and OF PMMA BONE CEMENTS fibre reinforcement is one possible way of impr--:!7ing their mech-

anical properties. There is, however, very little experience in the polymer industry with regard to the reinforcement of PMMA since it is generally used in non load-bearing applications. Commercial bone cements are all based upon PMMA, but the princi- pal problem as regards mechanical properties is brittleness. The effect of fibre addition, i.e. carbon, polyester, aramid, and two types of metal fibre, has been studied extensively at the research level (Mechanical Engineering Dept. at Trinity Coll-

ege, Dublin). Without having any historical data available, re- search programmes need to study factors such as fibre coating treatments, coupling agents, etc. before meaningful property meas- urements can be made. Fibre length and percentage are also cri- tical, since such fibres must either be incorporated into the polymerizing mixture or included in mixed form within the powder constituent. Even small amounts (2-4%) however,increase the dough viscosity to an extent where it is difficult to manipulate.

A different approach has been successfully used in Blackrock Cli- nic, Dublin, which involves inserting fibres as a rigid preform which is then infiltrated by cement in the bone cavity. The fib- res used are metal. Very good results have also been achieved using a woven polyester fibre.

GLASS FIBRE Ford Motor Co. has opted for a polyester resin reinforced with REINFORCED POLYESTER 17% glass fibre and containing a calcium carbonate filler for ENGINE MANIFOLD the manifold of its new 1.8 litre diesel engine. The glass fib-

res used are 12 mm in length. Moulding is carried out by the fusible metal core method. The manifold is linked to the cylin- der head by a short-tract aluminium manifold. A considerable weight-saving is achieved.

PATENTS

Us 4,769,443 STABILIZERS Ciba-Geigy Priority Date: 23 September 1983

Polymeric compounds containing piperidine radicals.

Cont./......

ADDITIVES FOR 0 1989 Elrevier Science RibliBhen Ltd., F.ngland./89/$0.00 + 2.20

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